From the FT piece:
UK: The most analysed and debated governance environment anywhere. The unitary board model survives, but since the recommendations of the Higgs report in 2003 there are more non-executives (and fewer executives) around board tables than in the past. The chairman and chief executive roles are usually kept separate.
US: Also a unitary board model, but with chairman, chief executive (and president) roles more often than not being held by the same person. A longer tradition of non-executive dominance of the boardroom. There is, however, a growing sense that Sarbanes-Oxley went too far and needs to be refined.